1. Field of the Invention
Example embodiments relate to a semiconductor device and a method of manufacturing the same and, more particularly, to a single electron transistor and a method of manufacturing the same.
2. Description of the Related Art
In order to increase a degree of integration of a semiconductor device, the size of unit cells should be reduced. However, various technical difficulties may arise in attempting such a reduction. Further, even when the sizes are reduced, unexpected problems may be undesirably generated. For example, electrons in a channel region may be decreased in number to several tens of electrons, and a ratio of the number of electrons corresponding to statistical errors to the number of total electrons operating in the unit cells may be increased, thereby affecting a reliability of the operations of the unit cells. Thus, there is a demand for unit cells having a structure suitable for a high degree of integration.
One approach to achieving a high degree of integration is to employ a single electron transistor (SET), in which each electron may be controlled. In a SET, movements of a single electron may be controlled by adjusting a voltage applied to the transistor and the movements of the single electron may serve as a switch. For example, when a semiconductor particle having a size of about several nanometers to about several tens of nanometers, i.e., a quantum dot, is placed in a region between a source region and a drain region, a single electron may enter and leave the quantum dot by a single electron charging effect, such that an on-state and an off-state may be generated, which serves as a switch. When the SET is compared to a conventional metal-oxide-semiconductor field effect transistor (MOSFET), the number of electrons required for performing the same action in the SET may be much smaller than that required for the MOSFET, and thus power consumption may be decreased using the SET. Additionally, a reliability of the SET may be improved because each of the electrons may be controllable.
However, quantum dots are difficult to form uniformly with conventional techniques, and thus the SET has not been made easily manufacturable. In particular, forming a quantum dot having a size of about 10 nm or less presents difficulties using known photolithographic approaches. Moreover, the formation of quantum dots having a desired size using an e-beam direct writing method may be difficult because of the proximity effect.
Thus, there is a need for a method of reproducibly forming a quantum dot having a controlled size, e.g., several nanometers, in a SET. Further, there is a need for a method of forming a quantum dot in a desired location in the SET. Preferably, such a method would provide a quantum dot having a size of several nanometers in a gate-all-around (GAA)-type transistor, wherein a channel region is surrounded by a gate electrode in order to decrease short channel effects.